The invention relates to a circuit arrangement for dual bus line for the transmission of differential signal voltages, each individual bus line of which is connected to a different input of a differential amplifier which is connected to a first pole and to a second pole of a feed voltage and the operating capability of which is restricted if the voltages at the two inputs are within a dead voltage range which is limited by the voltage at one pole of the feed voltage and by a voltage between the two poles.
Dual bus lines for transmitting differential signal voltages are generally known and are used for increasing the protection of the signal voltage transmission against interference because an interference signal acting on both bus lines generally changes the signal voltages on both bus lines essentially in the same direction and by the same amount so that the difference between the signal voltages on both bus lines is essentially retained and the information transmitted by this means is not disturbed. In some cases, however, the interference signals acting on such a dual bus line can be of such a magnitude that the voltages at both inputs of the differential amplifier connected to the dual bus line fall into the dead voltage range within which the differential amplifier no longer operates properly. The same effect can also occur if, due to an interference pulse on the feed voltage of the differential amplifier, its dead voltage range, compared with the signal voltages on the dual bus line, shifts to such an extent that these two fall into the dead voltage range. As a result, the differential amplifier can produce wrong output signals or its speed of response to changes in the signal voltages on the dual bus line can be impaired.